Liquid composition



Oct. 10, 1939. F. M. CLARK 2,175,877

LIQUID COIPOSII'ION Filed Sept. 30, 1936 Fig. l. Fig-Z.

*Q g 4000 4000 3 i 0v-4000-z0/0 0 /0 :0 00 40 00 0 4 a /2 /0 20 24 20 a: 00 40 44 40 TEMPERATURE PRUPO/FT/ON Inventor:

Frank MClark,

His Attorney.

Patented Oct. 10, 1939 PATENT OFFICE LIQUID COMPOSITION Frank M. Clark, Pittsfield, Mass., asslgnor to General Electric Company, a corporation of New York Application September 30, 1936, Serial No. 103,313

7 Claims.

The present application comprises liquid compositions of neutral oily consistency characterized by low viscosity at low temperature and more uniform viscosity-temperature relation than is normally associated with ordinary mineral oil or vegetable oil compositions, such as are used for lubricating, electrical insulatingand other industrial purposes.

It is one of the objects of my invention to 10 provide oily liquids suitable for cooling and dielectric purposes in electric devices, such as transformers. I

Another object of my invention is to provide low viscosity liquids of superior characteristics for use in electric cables of the liquid-filled type,

It is a further object of my invention to provide an improved liquid dielectric lmpregnant for capacitors whereby the electric capacity is materiall'y increased and the electrical operation at low temperature improved.

Still another object is to provide an improved liquid dielectric for are interrupting devices. Many arc interruption devices operate efilcient- 1y only when they are provided with liquids of low viscosity. This is especially true for those are interrupting devices which are constructed to open an electric circuit within a definite number of alternations of voltage on alternating current circuits. Even the lowest viscosity niineral oil having a required resistance to ignition within a prescribed limit of temperature has such increased viscosity at temperatures below room temperature, especially at temperatures as low as 30 C. and lower, that it constitutes a serious 5 obstacle in the operation of such devices.

It is also an object of my invention to provide compositions of superior lubrication characteristics. My improved liquid compositions not only have minimum viscosity change with temperature but also have as well superior extreme pressure lubrication characteristics as will hereinafter be shown. As a consequence of my invention I have provided lubricant and dielectric compositions of low pour point.

Other and important objects and applications of my invention will appear hereinafter.

The essential ingredients of my novel compositions are oily liquid materials of mineral or vegetable or synthetic origin in combination with 50 one or more alkyl phosphates, this term being used to designate such phosphates in their ordinary, unsubstituted form. Such compositions normally should contain by weight about 5 to 25 per cent of the alkyl phosphate, but such ingredi- 55 ent is not necessarily restricted to such limits.

Examples of oily materials constituting an essential ingredient of the compositions of this invention are mineral oils of the type in general use in electric transformers, cables, capacitors, ars interrupting devices and the like; mineral oils in general lubrication use for automotive and other mechanical devices; vegetable oils such as castor and linseed oils, synthetic oily liquids of the ester type (for example, butyl stearate, or tartrate or phthalate), or other oily ester derivatives of the alkyl or phenyl hydrocarbon nucleii, or chlorinated oil liquids such as the chlorodiphenyl, chlorodiphenyl oxides and others hereinafter designated.

As illustrative of the second ingredient used in combination with the foregoing materials, are alkyl phosphate esters, such as the ethyl, propyl or butyl esters, or combinations thereof. Such esters may be designated, generally, by the empirical formula RPO4, wherein R. comprises an alkyl radical containing not exceeding four (4) carbon atoms. For some purposes tributyl phosphate is preferred.

In the accompanying drawing Fig. 1 is a graph showing the viscosity characteristics of mineral oil compositions embodying my invention over a range of temperatures; and Fig. 2 is a graph showing the viscosity variation of a composition embodying my invention with changes of proportion of the ingredients.

In the graph of Fig. 1 temperature values are plotted as abscissae over a range from about C. down to the lowest temperatures encountered climatically. The curve A shows the viscosities over a range of about 100 of a mixture by weight of 25 per cent of tributyl phosphate and 75 per cent of a mineral oil. The data given for a composition containing a light mineral oil such as commercially designated as 10C Oil. The viscosity of the mixture changes but little as the temperature falls from 50 C. to about 20 C. and then as the temperature continues to fall to about -40 C, the viscosity rises only to 600 sec onds Saybolt. The mineral oil unassociated with modifying ingredients on the other hand begins to rapidly increase in viscosity at about 0 C. Its viscosity-temperature characteristic is shown by curve B as rising to about 10,000 seconds Saybolt at -40 c.

As shown by curve C a mixture of equal parts -by weight of tributyl phosphate and mineral oil has an even lower viscosity at very low temperatures. At -45 C. the viscosity of this mixture is still below 400 seconds Saybolt.

A particular composition adapted for use in the type normally used in electric transformers and 25 per cent by weight of the tributyl phosphate. Such a composition has the following properties:

Viscosity at -4() C 590 seconds Saybolt Universal Viscosity at +3'Z.8 C... 46 seconds Sayboit Universal Viscosity at 100 C 35 seconds Sayboit Universal Graidty at lob/15.5 C- .905

Condition Clear point 136 Burn point 108 C.

Four point Lower than -50 C.

Dielectric strength 33 RV.

Because of its improved viscosity-temperature characteristics coupled with the higher burn point than that normally associated with the usual transformer oil, such a composition has been found particularly well adapted for electrical insulating use in electric devices. One of my improved compositions when used in an arc interrupting device in which speed oi circuit interruption is of major importance resulted in a speed of operation at temperatures in the range of about -40 to -50 0., approximately 66 per cent over the normal speed obtained with the low viscosity mineral oil which had been used.

Compositions comprising mixtures of castor oil and tributyl phosphate further illustrate the present improvement. The relatively high pour point oi castor oil (about l C.) limits its use as a lubricant and as a liquid dielectric material in electrical devices. By the addition of t cutyi phosphate, or equivalent ester phosplate, to castor oil the viscosity at low temperatures is materially decreased. in the following table are compared viscosities at various temeratures also pour point oi two such mixtures with castor oil such as ordinarily obta'nsd, that unmixed with any modifier (designated as product 3):

Trib- Viscosity Pro Castor utyl Pour duct oil phospoint photo 100. 37.8 25 -l7 -25 Percent Percent 0. C. C. C. C. 75 25 35 4 378 860 52, 000 l 50 50 -69 47 128 196 30, 000

Patent 2,0375% patented April i936, have described compositions of mineral oil and chlorinated diphenyl. i prefer to employ liquid chlorinated diphenyl compound containing about 54 per cent chlorine (corresponding substantially in composition to pentachlor diphenyl) although some chlorinated compounds or lower and higher chlorine content be present. As described patented May 19,

ordinarily obmixture of armor? various isomers of pentachlor diphenyl. Such mixtures remain liquid at a lower temperature than a composition consisting of but a single isomer. Pentachlor diphenyl as ordinarily pro-- pared, is a viscous liquid having a'viscosity of about .8 to 50 seconds Saybolt at 100 C. and about 11,000 seconds Saybolt at 25 C. The pour point of this product is approximately 10 C.

When this material is compounded with even as little as 5 to per cent by weight of tributyl phosphate, then the low temperature characteristics are remarkably changed. The viscosity is lowered materially by the presence of even a few per cent of alkyl phosphate, as shown in Fig. which shows a graph D of the relation of viscosity at 25 C. of pentachlor diphenyl containing various proportions of tributyl phosphate.

Decreased viscosity of these compositions is accompanied by lowered pour points as shown in the following tabulation showing the pour points of three mixed products compared with chlorinated diphenyl (product 4) unassooiated with phosphate ester:

. Chlor 'lributyl Your Product diphenyl phosphate point Percent Percent C.

100 0 +10 85 10 75 25 22 5O 5O F 7) Such mixtures are of particular utility as impregnants in capacitors. A given capacitor containing lirait paper when impregnated with pentachlor diphenyl as described in my prior Patent 2,041,59 (product 4) has a capacity of 5 microiarads. When product 6 (25 per cent of tributyl phosphate) is introduced in its place in such capacitor, the capacity is found to'be 8 microfarads. When product 7 is employed the capacity is still further increased to approximately 11 microfarads. At temperatures below about 0 C. the capacity of capacitors impregnated with chlorinated diphenyl falls, due to solidification, to about '75 per cent of their original values. The drop in capacity of capacitors impregnated. with mixtures containing tributyl phosphate is eliminated down to temperatures as low as the pour point of the mixtures.

in place of chlorinated diphenyl other similar compounds may be used as the oily base. For example, I may use chlorinated diphenyl ketone (described in U. S. Patent 2,012,301 of August 2'7, 1935) or chlorinated polyphenyl methane (described in U. S. Patent 2,012,302) or chlorinated dibenzyl (described in U. S. Patent 2.0333512, patented March 10, 1936) or chlorinated diphenyl oxide (described in my pending application Serial No. 73,595 filed April 9, 1936). All of these chlorinated compounds may be considered for the purpose of this invention as being chlorinated derivatives of diphenyl.

illustrative of the lubricant use of my im proved compositions are mixtures made up in part of a lubricant mineral oil having a viscosity of 100 seconds Saybolt Universal at 100 C. and of approximately 1200 to 1400 seconds at 373 C. Such a composition when including 25 per cent tributyl phosphate by weight has a viscosity of 261 seconds at 37.8 C, a reduction of about 82 percent. When containing 50 per cent tributyl phosphate, the viscosity is reduced at 373 C. to less than (5 per cent of the normal oil viscosity. Such admixtures containing tributyl phosphate exhibit improved extreme pressure lubrication. With the selected lubricant oil the maximum load-carrying capacity was deter-, mined as 325 pounds for given conditions in a Timken lubricant tester. With only per cent by weight tributyl phosphate present the loadcarrying capacity was increased to greater than 1,000 pounds. Similar increased load-carrying capacity was observed for mixtures containing triethyl phosphate.

As a further illustration of the increase in the lubrication characteristics produced by compositions embodying my invention, the coeflicient of friction and unit pressure values obtained at the time of seizure of such compositions tested in the Timken tester are given in the following table from which the improved characteristics of my new compositions are evident:

0.102 Lubricant oil plus 5 percent Less than .076.

trlbutyl phos hate. 19,600. Lubricant oil p.us 5 percent Less than .05l' (35838;: than triethyl phosphate.

Greater than Limit of test machine. Actual lubricant breakdown and seizure of rubbing surfaces did not occur.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A composition of matter consisting of vegetable oil and from 25 to 50 per cent by weight of the whole of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding four carbon atoms.

2. A composition of matter consisting of mineral oil and from 25 to 50 per cent by weight of the whole of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding tour carbon atoms.

3. A composition of matter consisting of an oily chlorinated aryl compound selected from the group consisting of chlorinated diphenyl derivatives and from 25 to 50 per cent by weight of the whole of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding four carbon atoms,

4. A composition of matter consisting of pentachlor diphenyl and from 25 to 50 per cent by weight of the whole of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding four carbon atoms.

5. A composition of matter consisting of castor oil and from 25 to 50 per cent by weight of the whole of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding four carbon atoms.

6. A composition of matter consisting of mineral oil and from 25 to 50 per cent by weight of the whole of tributyl phosphate.

7. A liquid composition having a low and substantialiy uniform viscosity over a range of temperatures below 0 C., said composition consisting by weight of a liquid, oily organic lubricant or dielectric compound of lubricating oil range of viscosity, said base normally tending to become highly viscous at temperatures below 0 C., and about 25 to 50 percent of an alkyl phosphate ester having the empirical formula RPO4, where R comprises an alkyl radical containing not exceeding four carbon atoms, said phosphate ester being incorporated with. the said oily base for the purpose of decreasing the viscosity of the latter at temperatures below 0 C.

FRANK M. CLARK. 

